Enzymes are specific proteins of living tissues that act as biocatalysts. Enzymes can accomplish those reactions at normal temperatures and pressure which would otherwise require expensive, energy demanding high temperature and/or pressures, or might not be possible at all. That is why, use of enzymes in industries is growing.
Many micro-organisms produce extra-cellular enzymes. They are chiefly hydrolasesand are involved primarily in the degradation of macromolecules to units capable of being taken into the living cell. With the versatility of micro-organisms in producing enzymes, new methods of making many industrially important chemicals are being explored.
Current developments in biotechnology are yielding new applications for microbial enzymes. In addition to the conventional applications in food and fermentation industries, microbial enzymes have attained significant role in biotransformations involving organic solvent media specially bioactive compounds. Alongwith the use of micro-organisms to produce biomass and microbial metabolites, microbial cells may be used to catalyse the conversion of a compound into a financially more valuable compound. Microbial processes have the advantage of specificity over the use of chemical reagents and of operating at relatively low pressures and temperatures.
An important enzyme having various industrial applications is tannase (tannin acyhydrolase), which is an extra-cellular enzyme falling under the hydrolase group of enzymes. Tannins are water-soluble, phenolic compounds with molecular weight (500–3000) that have the property of combining with proteins, cellulose, gelatin and pectin and can be classified into two distinct groups based on their structural configuration, the hydrolysable tannins and the condensed tannins.
Tannase is widely used in the food and chemical industries. Further, tannase is used in wine making where it hydrolyses chlorogenic acid and quinic acid, which favourably influences taste in, the process of wine making. Tannase also has potential in the manufacture of acorn wine. Tannase is also used alongwith lactase to treat grap juice and grape musts
So as to remove phenolic substances for stabilization of the beverage. Tannase significantly reduces chill haze formation in beer. Disclouration and haze development during beer storage could be prevented by the enzymatic hydrolysis of wort phenolics with tannase.
Further, tannase is used in a preconversion treatment of fresh green tea flush in the production of instant tea. Tannase is also used in the determination of the structure of naturally occurring gallic acid esters.
Tannin acyl hydrolase commonly called tannase catalyzes, the hydrolysis of ester and depside bonds in such hydrolysable tannins as tannic acid, thereby releasing glucose and gallic acid. Gallic acid (3,4,5-Trihydroxybenzoic acid) finds various uses. In the pharmaceutical industry, gallic acid is used in the manufacture of trimethoprim. It is an antibacterial and is administered jointly with sulphonamide and together provide a broad spectrum action for medical treatment. TMP inhibits dihydrofolate reductase thereby blocking transformation of dihydrofolate to tetrahydrofolate. The consumption co-efficient of gallic acid in the manufacture of trimethoprim is 4.8. In the tannery industry gallic acid is used for homogenization of tannins, for the preparation of high grade leather tannins. Gallic acid is also used in the manufacture of ordinary writing inks and dyes, as a photographic developer. It also finds use in the enzymatic synthesis of gallic acid esters like propyl gallate, which is mainly used as an antioxidant in fats and oils, and also in beverages. It is used in the testing of mineral acids, dihydroxy acetone, and alkaloids, and as a synthetic intermediate for the production of pyrogallol which is used for the production of pyrogallol which is used for staining fur, leather, hair, etc.
Use of various fugal species to produce tannase is known in the art. A number of micro-organisms including bacteria like (Bacillus pumilis, B. polymyxa, Corynebacterium sp., Klebsiella pneumoniae) fungi (Ascochyta sp. Penicillium sp.) & yeasts (Candida sp.) have been reported to produce tannase.
Production of tannase by a strain of Aspergillus niger was reported by Tourrat et al. They found tannase activity was maximum when fermentation was carried out in submerged culture at a constant air flow. The enzyme activity was determined by gas chart method and the maximum enzyme activity was reported to be 5.5 n Kat/ml. R. Banerjee et.al, has reported the activity of tannase biosynthesis by a newly isolated R. oryzae. The experimental conditions were optimized in shake flask cultures. Maximum enzyme activity was found to be 6.12 U/ml.
R. Banerjee et al have also reported the production of tannase by solid state fermentation using R. oryzae. 
Production of extracellular tannase by bacterial strains (B. polymyxa, B. puminis, klebsiclla pnon & Corynebacterium) within few hours of culture with simultaneous release of gallic acid & glucose has been reported by Deschamp et al.
Raj Kumar et al. have reported the isolation, purification and some properties of Penicillium chrysogcnum tannase.
The enzyme is stable up to 30 C. and within the pH range of 4.0–6.0 Km value was found to be 0.48×10−4M with tannic acid as the substrate. Metal salts at 20 Mm inhibited with enzyme.
Continuous production of gallic acid from tara tannin in a bioreactor using Penicilium chrysogenum immobilized on sodium alginate & CaCl2 is known from Yamada et al. They have also reported the use of tannase in wine making industry.
Not much is known about the biotransformation of tannins to gallic acid. The literature available mainly relates to chemical process wherein the yield of gallic acid is was very low. Kar, B. et al have reported the biotransformation of tannins to gallic acid by SSF and SmF process using gallo seed cover and Rhizopus oryzae as the raw material.
However, the processes of the art suffer from various drawbacks ie they require a long time and the yield reported is also low.